10mm or 20mm, pressure difference?

Jognt · Jun 14, 2004

Im looking for a decent fan for my geforce 2 mx400 homemade heatsink, right now i have a papst 40*40*10 fan on it, i gutted an old 40mm fan to remove the dead spot a bit, but with that in place, more air was coming back via the blades, than via the heatsink fins...

I just spotted a 40*40*20 fan, also made by papst, and im wondering if the extra height adds pressure.. because id like to have enough pressure for the fan to efficiently blow through the HS (well... more efficient than it is now

)

mtb856 · Jun 14, 2004

Well, I'm stretching a little... but if you take a 25mm thick fan(a case fan) and a 38mm thick fan (a Delta) the 38mm usually puts out quite a bit more pressure than the 25mm. I'm assuming that the same holds for the fans that you're talking about, although it does depend on the rpm's that they are running at.

Jognt · Jun 14, 2004

yes, i thought that higher fins might give more pressure, but i like to be sure before i spend more money than i make (which is 0.. no time for a job with school)

the 20mm fan comes in two flavours:
7.9 CFM 8100rpm (29dBA)
5.9 CFM 6000rpm (18dBA)

my current 10mm fan runs at 5400rpm (4.7CFM @ 26dBA)

if i get the 5.9CFM one, the noise will also be reduced

since im trying to build a silenced PC

If the pressure increases, can the increase in pressure actually be noticed?

mtb856 · Jun 14, 2004

Where do you go to school? If you're in college, then it'll probably have a tutoring lab. I'm a math and physics tutor (also a lifeguard during the summer)... all I do is walk out of class and go up one floor to go to work

Easy job too, answering homework questions for the most part.

Jognt · Jun 14, 2004

hmm, tutor

may not be a bad idea

i dont know if what i do can be called college, but im 17 and im a year older than all the others in my class, so i dont know what that would be in an american school :-/

Even though i could tutor, it would be next schoolyear, so money is still hard to come by (going to try and get hired at a local PC store though) so if these higher fans give a decent increase in pressure, then i may try to get my money together to by one.

(damn, if only i didnt smoke

then id have a whole bank account with money

)

mtb856 · Jun 14, 2004

I'd say that there's an easy solution to that problem, but I'm addicted to caffiene/coffee so I'm in no place to mention it. If I don't get coffee every morning I get a migraine.

archilochus · Jun 14, 2004

Jognt, Here's a link to a Papst PDF...It shows the pressure diff. between the diff. fans they make...40mm that is..

Air Flow m3/h

CLICK HERE :thup:

Jognt · Jun 15, 2004

thanks arch! ill take a good look at it now

edit: which one of those tabels is for pressure?

the 412F (10mm) and the 412 (20mm) are the fans im interested in, it shows the airflow in M3/h and in cfm, and the voltages, etc, but i dont know where it explains the pressure <_< ( and im not too good at interpretting that graph :-/

)

archilochus · Jun 15, 2004

SOURCE LINK

Fan Performance

While the selection of a ventilation unit from the output tables to perform under free air conditions is a simple matter, it is useful to know the rudiments of fan performance against some resistance to airflow, such as ducting and filters, or even sufficient free area for the passage of replacement air into a room from which the unit is extracting.

Characteristic Curve

Any particular fan design has its own characteristic curve, which is a graph made by plotting a number of test points showing volume delivered against different resistances. Volumes are measured in cubic metres per second (m³/s), which for the sake of convenience in calculations in our class of work is converted to cubic metres per hour (m³/h, and pressures are measured in Pascals (Pa.).

Pressure

The total pressure produced by a fan is made up of the static pressure, that is the useful working pressure available for overcoming the resistance of a ventilating system and velocity pressure, which is the pressure due to the speed of the air. These fan pressures are of a very low order and that is the reason for using the unit of Pascals instead of kg/m² or g/cm².

Pascals

One Pascal is a pressure equal to a force of one Newton applied over an area of one square metre (= 1 N/m²). As one Newton approximately equals a force of 0.1 kg, one Pascal = 0.1 kg/m² or 0.0000 1 kg/cm² (=0.000 145 lb/in²). Other expressions used for resistance are inches water guage (1Pa = 249.1 in.wg) and mm waterguage, an intriguing combination of metric and imperial, 1mm wg = 9.8Pa.

archilochus · Jun 15, 2004

Jognt, look at "Curve" on the chart..(PDF) Left of "TYPE"..Those numbers reflect on the graph below...1 being lowest pressure..5 , highest pressure..The 40 x 40 x 20( 412H ) has the highest pressure..So yea, the pressure increases with the thickness of the fans body as thought..

At least in this case.

mtb856 · Jun 15, 2004

Ah, good... arch was able to find the answer. I'm glad I didn't have to dig out my old physics books on this one

. It would be interesting to see if that applies to all fans or if it's built in by the fan manuf.

Jognt · Jun 16, 2004

thanks arch and mtb856

ill be getting this fan then

dont look at me with graphs

all my life math was my best class, but this year i passes with a 4.6 (scale of 10) so i suck now

archilochus · Jun 16, 2004

You might need a little tutoring..

Looks up

..

mtb856 · Jun 16, 2004

Hey Jognt, one of the best suggestions a teacher ever gave me was "STUDY". Especially, when (are you in college, Jognt?) you get to college math... there are no similiarities between high school and college math ( at least in the States). Here, most high school math is the dirt speck on top of the iceberg, most of the high schoolers that I see didn't study in H.S so they think that they can get away with it in college... and they fail horribly. I spend about a week before a test... 5-6 hours a day per subject studying (at least in math and physics).

Also, if you have free tutoring over there... use it if you get stuck. Most of the people I see just need a different way to look it in order to understand. Anyway, this wasn't intended to slam your math ability or your studying habits, just to give you a heads up if you aren't in higher level math yet.

later

Jognt · Jun 16, 2004

wow... so that was what i was doing wrong.. when i have/had a math test, the night before, 30 minutes before i went to bed, id read through the book some more.. so thats why i always get low grades lol

lol @ archilochus :santa2:

archilochus · Jun 16, 2004

mtb856 · Jun 16, 2004

yeahhhhhhhhh, that might of had something to do with it

10mm or 20mm, pressure difference?

Jognt

All round good guy

mtb856

Member

Jognt

All round good guy

mtb856

Member

Jognt

All round good guy

mtb856

Member

archilochus

THE Senior FANMAN

Jognt

All round good guy

archilochus

THE Senior FANMAN

archilochus

THE Senior FANMAN

mtb856

Member

Jognt

All round good guy

archilochus

THE Senior FANMAN

mtb856

Member

Jognt

All round good guy

archilochus

THE Senior FANMAN

mtb856

Member

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